abstract: Identification of early damage in polymer composite materials is of significant importance so that preventative measures can be taken before the materials reach catastrophic failure. Scientists have been developing damage detection technologies over many years and recently, mechanophore-based polymers, in which mechanical energy is translated to activate a chemical transformation, have received increasing attention. More specifically, the damage can be made detectable by mechanochromic polymers, which provide a visible color change upon the scission of covalent bonds under stress. This dissertation focuses on the study of a novel self-sensing framework for identifying early and in-situ damage by employing unique stress-sensing mechanophores. Two types of mechanophores, cyclobutane and cyclooctane, were utilized, and the former formed from cinnamoyl moeities and the latter formed from anthracene upon photodimerization. The effects on the thermal and mechanical properties with the addition of the cyclobutane-based polymers into epoxy matrices were investigated. The emergence of cracks was detected by fluorescent signals at a strain level right after the yield point of the polymer blends, and the fluorescence intensified with the accumulation of strain. Similar to the mechanism of fluorescence emission from the cleavage of cyclobutane, the cyclooctane moiety generated fluorescent emission with a higher quantum yield upon cleavage. The experimental results also demonstrated the success of employing the cyclooctane type mechanophore as a potential force sensor, as the fluorescence intensification was correlated with the strain increase. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2014

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Agradecemos a compreensão. on 2016-06-09T16:17:55Z (GMT) / Submitted by RUBEN FELIPE ARTURO OBLITAS TORRICO null (ro1485@my.bristol.ac.uk) on 2016-06-09T16:57:07Z No. of bitstreams: 1 Dissertacao.pdf: 2188934 bytes, checksum: 633201227bb5f6a322e3d0dec8645d34 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-06-13T20:07:22Z (GMT) No. of bitstreams: 1 torrico_rfo_me_araiq_par.pdf: 757530 bytes, checksum: 9e239d69620a743d05fb3a39c914d9bc (MD5) / Made available in DSpace on 2016-06-13T20:07:22Z (GMT). No. of bitstreams: 1 torrico_rfo_me_araiq_par.pdf: 757530 bytes, checksum: 9e239d69620a743d05fb3a39c914d9bc (MD5) Previous issue date: 2016-04-15 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este projeto visa a investigar a relação entre a estrutura e as propriedades dos materiais epoxi-silica preparados pelo método sol-gel. Os híbridos foram preparados pela reação de cura entre o poly(Bisphenol A-co-epichlorohydrin) (DGBEA) , e o dietil triamina (DETA) assim como pelo processo Sol-Gel de hidrolise e condensação entre GPTMS (3-Glycidoxypropyl)methyldiethoxysilane) e TEOS. Ressonância magnética nuclear (RMN), espectroscopia de fotoelétrons de raios X (XPS), espalhamento de raios X a baixo ângulo (SAXS), espectroscopia de Infravermelho e RAMAN, microscopia de força atômica (AFM) assim como termogravimétria foram utilizadas com o proposito de investigar a morfologia e as propriedades estruturais do material. Finalmente as propriedades anticorrosivas dos filmes foram testadas em uma solução salina por meio de espectroscopia de impedância eletroquímica (EIS). Durante a fase inicial do projeto diferentes amostras com diferentes concentrações de TEOS foram preparadas. A estabilidade térmica como as propriedades anticorrosivas foram testadas. Os resultados mostraram que para maiores concentrações de TEOS, as propriedades anticorrosivas e térmicas dos híbridos melhoram significativamente. Vários resultados interessantes foram obtidos, para híbridos com razoes molares de TEOS : GPTMS : DGBEA = 1 : 1: 1, tendo módulos de impedância de até 1010 Ω cm-2. Durante a segunda fase do projeto, duas series de amostras com concentrações diferentes de GPTMS a TEOS foram preparadas. As propriedades estruturais foram obtidas por meio de Espectroscopia Infravermelho, Raman, RMN e XPS e espalhamento de raios X a baixo ângulo. A hidrofobicidade assim como as propriedades térmicas foram avaliadas por meio de testes de molhabilidade e análise termogravimétrica. Finalmente as propriedades anticorrosivas dos filmes em contato com solução salina foram testadas por meio de espectroscopia de impedância electroquímica. / This work aims to investigate the relationship between the structure and the properties of the sol-gel prepared epoxy-silica materials. The organic-inorganic hybrids were prepared from the curing reaction of poly(Bisphenol A-co-epichlorohydrin) (DGBEA), with Diethyltriamine (DETA) and (3-Glycidoxypropyl)methyltriethoxysilane) (GPTMS) combined with the sol-gel hydrolysis and condensation reactions between Tetraethoxysilane (TEOS) and GPTMS. Nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), Infrared and Raman spectroscopy (IR), Atomic force microscopy, as well as thermogravimetry (TG) have been used with the purpose to investigate the morphological and structural properties of the material. Finally the anticorrosive properties of the hybrid coated carbon steel were evaluated in saline solution using electrochemical impedance spectroscopy (EIS). During the initial phase of the project different samples with increasing concentrations of TEOS have been prepared and their thermal stability as well as their anticorrosive properties were tested. It was found, that for increasing TEOS concentration, the hybrid’s anticorrosive and thermal properties can be improved. Several interesting results were obtained for hybrid coatings at a TEOS : GPTMS : DGBEA = 1 : 1 : 1 ratio, having an impedance modulus of up to 1010 Ω cm-2. During the second phase of the work, a series of epoxy-silica hybrids were synthetized varying the concentrations of GPTMS and TEOS. Their structural properties were characterized by means of Infrared, Raman, solid NMR and XPS spectroscopy. Their hydrophobicity as well as their thermal resistance were evaluated using the drop shape analysis and thermogravimetry. Finally the anticorrosive properties of the coatings in saline solution were tested using electrochemical impedance spectroscopy.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Os primers sÃo tintas primÃrias que funcionam como fundo anticorrosivo quando aplicados sobre metais. As suas propriedades anticorrosivas devem-se os pigmentos usados na sua composiÃÃo, sendo os mais comuns o zarcÃo, o cromato de zinco, o Ãxido de ferro e o pà de zinco. As tintas à base de resina epoxÃdica sÃo bastanteutilizadas como primers, pois apÃs a cura estas tornam-se impermeÃveis e, quandosÃo associadas a pigmentos com propriedades anticorrosivas, aumentam a resistÃnciado substrato à corrosÃo. PelÃculas secas de tintas-primers formuladas com resinaepoxÃdica DGEBA (Ãter Diglicidil de Bisfenol A), reticuladas com umapoliaminoamida (Versamid 125), e com dois pigmentos anticorrosivos, um tÃxico (cromato de zinco) e outro nÃo-tÃxico (sÃlica trocadora de cÃlcio) foram estudadas atravÃs das tÃcnicas de termogravimetria (TG), infravermelho (FTIR) e microscopia eletrÃnica de varredura (MEV). AtravÃs de TG foram determinados parÃmetros cinÃticos, como a Energia de ativaÃÃo, tanto pelo mÃtodo de Ozawa-Wall-Flynn, quanto de Kissinger. Verificou-se que o mecanismo de degradaÃÃo das tintas epoxidÃcas à alterado na presenÃa dos pigmentos. A estabilidade termo-oxidativa do primer com cromato de zinco, baseada nos valores de IPDT, à menor do que a do primer com o pigmento silica cÃlcio. A imersÃo dos primers em Ãcido clorÃdrico, nas concentraÃÃes de 10-5 atà 6,0M, reduz a estabilidade tÃrmica, sendo o mais afetado aquele contendo cromato de zinco. Neste ocorre a formaÃÃo de poros, detectados pela MEV. O uso do pigmento anticorrosivo sÃlica cÃlcio apresenta, alÃm da vantagem da nÃo toxidade, maior estabilidade termo-oxidativa e maior resistÃncia a ambientes Ãcidos do que o pigmento cromato de zinco. / The primers are primary anticorrosive dyes, with anticorrosive property due to the presence of appropriate pigment. The most common used anticorrosive pigments are zarcÃo, zinc chromate, iron oxide and zinc powder. Paints based on epoxy resin are very used as primers, because their impermeability and, when associated with anticorrosive pigments, the increase in the resistance against corrosion. Films of paint-primers formulated with DGEBA epoxy resin (Diglycidyl Ether of Bisphenol A), crosslinked with polyaminoamida (Versamid 125) , and with two anticorrosive pigments, zinc chromate (toxic) and calcium silicate (not toxic), were studied by thermogravimetric analysis (TG), infrared spectroscopy (FTIR) and scanning electronic microscopy (SEM). Kinetic parameters, such as activation energy, were calculated by TG, using Ozawa-Wall-Flynn and Kissinger methods. Change in the mechanism of epoxy paint degradation was observed in the presence of the two pigments. Primer with calcium silicate was more thermally stable than that with zinc chromate, based on IPDT values. The immersion of primers films in hydrochloric acid in the concentrations range from 10-5 to 6,0 M led to a decrease in the thermal stability. The most affected primer was that with zinc chromate, in which porous was detected by SEM after the immersion in acid solution. The primer with calcium silicate has the advantage of being more thermally stable and more resistant to acid attack, in addition to its more important ecological property, the non toxicity.

Orientador: Lucia Helena Innocentinni Mei / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-20T09:55:20Z (GMT). No. of bitstreams: 1 Carvalho_IviMartinsde_M.pdf: 1540327 bytes, checksum: 645ccaa60b4cb1206d1e1a77feb19416 (MD5) Previous issue date: 2012 / Resumo: Plastissois de PVC reticulados na presença de resina epóxi polifuncional foram obtidos através de espalmagem. Foi possível inferir que a presença de um acelerador tipo amina, ao menos nas condições de processamento utilizadas neste estudo, mostrou-se imprescindível para a ocorrência do processo de reticulação. Resultados de grau de reticulação mostraram que só houve formação de gel nas amostras onde o acelerador foi utilizado concomitantemente com a resina epóxi. Apesar da comprovação da reação química ser dificultada pelo grande número de diferentes sinais de FTIR presentes na formulação, resultados de teor de gel e módulo de Young parecem confirmar a hipótese de formação de uma rede tridimensional entre as moléculas do PVC e a resina epóxi, porém serão necessários estudos mais aprofundados no futuro para identificação do polímero hiper-ramificado formado / Abstract: Crosslinked PVC plastisols in the presence of polyfunctional epoxy resin were obtained from spreadcoating. It was possible to infer that the presence of an amine type accelerator, at least in the conditions used in this study proved to be essential for the occurrence of the crosslinking process. The results of reticulation degree showed that gel formation only happened in samples where the amine has been used concomitantly with the epoxy resin. Despite the evidence of chemical reaction is complicated by the large number of molecules present in the formulation, Young's modulus results seem to confirm the hypothesis of the formation of a three-dimensional network between the molecules of PVC and epoxy resin, but further studies are needed in the future to identify the hyperbranched polymer formed / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

Reinforced polymer composites consist of continuous fibers embedded in a polymer matrix. The matrix is usually a thermoplastic or thermosetting resin. When thermosetting matrices are cured during the manufacture of composite parts, residual stresses develop within the part during the manufacture due primarily the thermally and chemically induced volumetric strains imposed on them. This can lead to shape distortions and sometimes weakening of the structure itself. Curing is the manufacturing process in which the thermoset resin is transformed from a liquid to a solid material. The molecular mechanisms involved in this process are quite complex and not well understood. In the macro-level, in addition to volumetric strains, heat is also generated since most thermoset polymerization reactions are exothermic. The mechanical properties of the thermoset also undergo dramatic changes. The material changes from an initial liquid state to a rubbery gel and finally to a vitrified glassy state. In modern day composite manufacturing, to accommodate for the shape distortions caused due to residual stress formation, the mold geometry is compensated. To do this, accurate predictions of the distortion behavior is preferred via computer simulations. This in turn requires simple mathematical models that can replicate the complex processes that take place during manufacture. One such process that requires attention is the curing of the thermoset. While models exist that assume elastic behavior during cure, they are not accurate throughout the entire cure process. Models based on viscoelastic material during cure offer better prospects in this perspective. However, currently models that are based on full viscoelasticity are either not well defined or are computationally tasking. Viscoelastic materials can be classified further in to thermorheologically simple and complex materials depending on their molecular weights. In simpler terms, thermorheologically simple materials are those that obey the principles of time-temperature superposition (TTS). TTS requires that all response times (i.e., all relaxation or retardation time), depend equally on temperature. This is expressed using the temperature shift function. Master curves can be then generated extending the time scale beyond the range that could normally be covered in a single experiment. However to fully understand the development of viscoelasticity during cure it is also necessary that the effects of the degree of cure of the thermoset on these times be included in the model definition. This requires defining a cure shift function along with the temperature shift function. In the presented work, an attempt is made to develop a simplified methodology to characterize the viscoelastic material properties during curing. Two different methods are investigated in a DMTA instrument to determine the effects of curing on the glassy state of the resin system LY5052/HY5052. A cure shift function was identified in the process. Based on observations it was concluded that the total shift function could be possibly defined as a product of the temperature and cure shift functions. Unique super-master curves were generated as a result. However, these curves showed a dependency of the rubbery modulus on the degree of cure. Hence, in the second paper, the effect of the degree of cure on the rubbery modulus was investigated. Subsequently a model was reformulated from an existing one and this was used to further simplify the super-master curves. Following dynamic testing, it was necessary that macroscopic testing is performed to corroborate the results. The macroscopic experiments utilized for this purpose was stress relaxation tests to determine the viscoelastic Poisson’s ratio of neat resin. The Poisson’s ratio in particular is an important property to study, since it’s interaction with the fiber during curing is critical in the study of residual stresses. The focus of the study is to determine if there is a dependency of the Poisson’s ratio on degree of cure and whether master curves can be generated by horizontal shifting of data. Literature pertaining to the dependency of the Poisson’s ratio on degree of cure is scarce. If appropriate horizontal shifting can be performed, it can be easily compared to the results from dynamic testing to check if the shift factors are truly universal. Also presented is a brief study of the effect of degree of cure and time on the development of viscoplastic strains during curing. This is done by performing creep tests on composite specimens with varying degrees of cure. The experimental results were then used to validate the well-known Zapas-Crissman model for viscoplastic strain evolution with time and investigate how it is influenced by the cure state.

Electrical trees have long been the interest of the electrical insulation community due to their role in power systems equipment failure at locations where high divergent fields might arise due to impurities, contaminants or voids. Even through trees take a long time to grow in real life, they can be grown experimentally in shorter times under various conditions so that their growth characteristics can be investigated. Different samples have been fabricated to investigate the effects of interfaces in electrical tree propagation. Initially, the impact of an interface perpendicular to the electric field, and the interface position, thickness and/or composition on the polymer’s lifetime was investigated. In the results acquired, the positive impact of interfaces positioned perpendicular to the electric field was evident: increasing the samples’ time to breakdown as well as the electrical tree inception time. Due to the encouraging results, further investigation has been focused on interface modification and how this might be used to control the electrical tree growth as well as the samples’ time to breakdown. Altering the interface’s surface roughness using a number of different methods was carried out. Results were graphically and statistically analysed so that the any conclusions are robust, and uncertainties clear. The statistical analysis used by generating regression model equations was a novel method to predict how different electrical tree parameters were affected/affecting by others. In this way the dielectric’s lifetime could be predicted with a certain level of confidence. The modification of the interface by coating the surface with either a thin layer of pure or nano-filled (hexagonal Boron Nitride) epoxy resin resulted in it being impervious thus preventing the electrical tree to propagate through it. This was a novel method that showed that specific modification methods can significantly enhance the dielectric’s lifetime when applied appropriately. Details of new sample fabrication techniques are described which enable better control of the materials and interfaces, and data on tree length growth characteristics are discussed.

La caractérisation et l’évaluation des propriétés physiques, chimiques, physico-chimiques et mécaniques sont un point important dans la compréhension du comportement des assemblages collés polymère/substrat. La spectroscopie diélectrique est une méthode de caractérisation efficace permettant d’étudier la dynamique moléculaire, et permettre aussi un suivi in situ de joints collés. La modélisation mathématique de résultats expérimentaux par la méthode de l’analyse par intervalle permet de s’affranchir de nombreux défauts de logiciels utilisés couramment (erreur expérimentale prise en compte dans les calculs du modèle, permet d’accepter ou de rejeter un modèle, …). Il a été démontré qu’en présence d’un substrat métallique, une compétition avait lieu entre la réaction de polymérisation et des réactions entre les monomères et les substrats métalliques, menant à une interphase (i.e. interface d’épaisseur non nulle) ayant des propriétés différentes des propriétés du même polymère en volume. Ces propriétés influent sur l’adhérence entre le polymère époxydeamine et le substrat d’aluminium. L’adhérence sera caractérisée par un test normé et reliée aux propriétés de l’interphase par diverses techniques. Des vieillissements de systèmes DGEBAanime/ aluminium ont été effectués. Durant ces vieillissements, des tests destructifs et non destructifs ont été effectués afin d’avoir un suivi sur les propriétés des interphases et interfaces de ces joints collés. Les résultats obtenus ont été mis en corrélation afin de pouvoir être capable par l’utilisation de tests non destructifs in situ, de pouvoir prévenir une rupture à l’interphase/interface entre l’adhésif et le substrat / Characterization and evaluation of physical, chemical, physico-chemical and mechanical properties are an important point in the comprehension of the behavior of bonded polymer/substrate assemblies. Dielectric spectroscopy is an effective method of characterization to study molecular dynamics, and also allow in situ monitoring of bonded joints. Mathematical modeling of experimental results by the method of interval analysis overcomes many shortcomings of commonly used software (experimental error taken into account, accept or reject a model ...). It has been shown that in the presence of a metal substrate, a competition was held between the polymerization reaction and the reactions between the monomers and metal substrates, leading to an interphase (i.e. non-zero thickness of interface) having properties different than these of the bulk. These properties influence the adhesion between the epoxy-amine polymer and the aluminum substrate. Adhesion will be characterized by a standardized test and related to the properties of the interphase by various techniques. The aging of DGEBA-anime/aluminum system have been done during this study. During the aging, destructive and non-destructive tests were carried out in order to have a follow-up on the properties of interfaces and interphases of these bonded joints. The results were correlated in order to be able to use an in situ non-destructive testing to prevent the rupture at the interphase/interface between the adhesive and the substrate

The generation of nuclear energy leads to the generation of contaminated, radioactive wastes. The current strategy in the UK is to dispose of high and intermediate level wastes to a geological disposal facility with no possibility for retrieval. The waste is contained in an encapsulation matrix, which is usually cement, however cement is unsuitable for certain waste types, for which epoxy resins have been proposed as an alternative. The radiation resistance of two candidate epoxy/amine resin formulations under repository conditions were tested with regards to the degradation of the backbone structure and the release of potential organic ligands from the polymer. The difference in the polymers was the choice of amine curing agent. Analysis of the polymer by infra-red spectroscopy and nuclear magnetic resonance spectroscopy revealed that the carbon nitrogen bonds are the most susceptible to radiation damage, regardless of the atmospheric and aqueous environment. The presence of an aqueous phase greatly reduces the availability of oxygen and reduces the rate of degradation when irradiated under an atmosphere of air. The properties of the aqueous phase has little effect on the degradation of the polymer. Thermal analysis revealed that the effects of the environment are limited to a thin surface layer of the polymer. Leachate analysis revealed that both organic and nitrogen containing compounds are leached from the polymer when irradiated in pure water. Under repository conditions however very little carbon and nitrogen is observed, suggesting that the calcium hydroxide present in repositories is capable of removing the leached species from solution. The generation of nitrate ions from air radiolysis over water is suppressed in the presence of the polymers, suggesting that nitrate is removed from solution by leached species or reaction with the polymer.

Epoxy resins are widely used materials in the industry as electrical insulators, adhesives and in aircrafts structural components because of their high mechanical stiffness, strength and high temperature and chemical resistance properties. But still, the influence of water uptake due to moisture adsorption is not fully understood as it detrimentally modifies the electrical and chemical properties of the material. Here ,we investigate the influence of water moisture uptake on the neat epoxy material by monitoring the change in the volume resistivity and dielectric properties of epoxy material at three different thickness configurations: 0.250 mm, 0.50 mm and 1 mm thicknesses. Gravimetric analysis was done to monitor the mass uptake behaviour, Volume Resistivity was measured to monitor the change in conductivity of the material, and the dielectric properties were mapped to characterise the type of water mechanism available within the material during two ageing processes of sorption and desorption. Two-stage behaviours of diffusion and reaction have been identified by the mass uptake analysis. Moreover, the plot of volume resistivity versus mass uptake has indicated a non-uniform relationship between the two quantities. However, the analysis of the dielectric spectrum at medium range of frequency and time has showed a change in the dipolar activities and also showed the extent to which the water molecules can be segregated between bounding to the resin or existing as free water

This thesis describes the effects of climatic factors, particularly humidity and temperature on the properties of macromolecular substances, but also others, such as UV radiation, wind, water and oxygen. Furthermore, we introduce the definition and distribution of macromolecular substances. The next section describes the basic properties of dielectric materials. Much of the text is devoted to the description, production, curing, properties and utilization of epoxy resins. The last part deals with climate factors in general terms.